1. Field of the Invention
The present invention relates to a disc cartridge that accommodates an information recording and/or reproduction medium, and more particularly, to a disc cartridge and a disc drive apparatus having an improved identification mechanism to identify types of discs.
2. Description of the Related Art
In general, a disc cartridge is used in a disc drive and accommodates a disc-type recording and/or reproduction medium, such as an optical disc or magnetooptical disc. The disc cartridge is widely used as a recording medium for multimedia such as video and sound as well as for text and images. With the continued development of multimedia, a disc cartridge having a large capacity is required. As such, various types of disc cartridges have been developed that accommodate a disc having an improved recording density. For example, in the case of a DVD-RAM, there are various types of discs such as a general single-sided type disc (where information is recorded on only one side thereof), a double-sided type disc (where information is recorded on both sides thereof, a single-sided, double-layer type disc (where two recording layers are formed on one side thereof), and a disc where a track pitch is relatively narrow as compared to the general single-sided type disc. Thus, a variety of type of disc cartridges which can accommodate the above discs having various types of recording density are provided.
However, when the recording density varies, a recording and/or reproduction method performed by a disc drive apparatus varies accordingly. That is, the disc drive apparatus performs a method of recording or reproducing information according to the structure of a track pitch of a disc or according to the type of a layer of a disc, such as a single layer or double layer. Thus, the disc drive apparatus needs a mechanism to detect the type of the disc when the disc cartridge accommodating the disc is inserted into the disc drive apparatus.
FIG. 1 shows a conventional mechanism to detect the type of a disc, an example of which is disclosed in Japanese Patent Publication No. 11-120733. Referring to FIG. 1, a magnet 5, which is used to identify a large capacity disc, is installed at a disc cartridge 1. The disc cartridge 1 rotatably accommodates a disc 2 in a case 3. A magnetic sensor 7, which detects the magnet 5, is installed at a disc drive apparatus 6. Thus, when the disc cartridge 1 is inserted in the disc drive apparatus 6, the magnetic sensor 7 detects a magnetic force of the magnet 5 to determine that the disc 2 in the disc cartridge 1 has a large capacity. Then, the detected result is transmitted to a controller (not shown) of the disc drive apparatus 6 so that the controller can control the recording and/or reproduction according to the type of the disc 2.
However, when a disc 2 has a small capacity, the magnet 5 is not installed. Thus, when the disc cartridge 1 accommodating the disc 2 having a small capacity is inserted in the disc drive apparatus 6, the magnetic sensor 7 does not detect a magnetic force. As such, the disc drive apparatus 6 determines that the disc 2 in the disc cartridge 1 is a disc 2 having a small capacity.
In the above conventional apparatus, since the type of the disc 2 is detected by the on/off state of the magnetic sensor 7 according to the presence or absence of the magnet 5, only two types of a disc (i.e., a high capacity or a small capacity) can be detected. Thus, to detect a variety of types of discs 2, the number of the magnets 5 should be increased. Accordingly, the corresponding number of the magnetic sensors 7 are installed so that the type of the disc 2 is detected using the ones of the magnetic sensors 7 that are turned on.
According to another method, by installing the magnets 5 having different magnetic forces according to the types of discs 5, the type of the disc 5 is detected. In this case, it is necessary to install a circuit that is accurate in detecting different magnetic force intensities instead of just detecting an ON and an OFF state.
According to these conventional apparatuses, increasing the number of the magnetic sensors 7 prevents manufacturing smaller and lighter disc drive apparatuses 6 while increasing the manufacturing cost and lowering productivity. Also, detecting the type of a disc 2 by using different magnetic forces needs an accurate circuit that exacerbates these problems. Further, when the magnetic force deteriorates, there is a possibility that the type of the disc 2 would be incorrectly determined.
Therefore, a disc cartridge and a disc drive apparatus having an improved, but simpler structure to detect the various types of discs is needed.